Miniature potentiometer



Jan. 21, 1964 R. o. MURRY 3119089 MINIATURE POTENTIOMETER Filed sep'z. 14, 1982 INVENTOR.

ROBI/P7 0. MUR/FV BY MJ W tral hole 14 therethrough, and a notch 16 in its edge.

United States Patent O 3,119,089 MENIATURE PGTENTTOMETER Robert O. Marry, Bnrlington, Iowa, assignor to International Resistance Company, Philadelphia, Pa. Filed Sept. 14, 1962, Ser. No. 223,771 8 Claims. (Cl. 338-174) The present invention relates to a miniature potentometer, and more particularly to a miniature trimmer potentiometer which is simple in construction and economical to manufacture.

For many types of electrical equipment it is desirable to use in the electrical circuit thereof a resistor the resistance value of which can be adjusted, but which can be set and maintained at a desired resistance value. Such resistors are commonly called Trimmer Potentiometersf With the increasing trend toward miniaturization of electrical equipment, it is desirable that such trimmer potentiometers be as small as possible. Also, such potentiometers should be of simple construction so as to be economical to manufacture.

lt is an object of the present invention to provide a novel trimmer potentiometer having a film type resistance path.

It is another object of the present invention to provide a novel potentiometer which can be made in very small slzes.

It is still another object of the present invention to provide a novel potentiometer which can be set and maintained at a desired resistance value.

It is a further object of the present invention to provide a potentiometer having a variable range of maximum resistance values.

It is a still further object of the present invention to provide a potentiometer which is simple in construction so as to be economcial to manufacture.

It is another object to provide a potentiometer in which the position of the terminals can be adjusted to permit ease of securing the potentiometer in a desired circuit.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a top plan view of the potentiometer of the present invention.

FIGURE 2 is an exploded perspective view of the potentiometer of the present invention.

FIGURE 3 is a sectional view atken along line 3-3 of FIGURE 1.

FIGURE 4 is a perspective view of a modification of the potentiometer of the present invention.

FIGURE 5 is a side elevational view of the modification of the potentiometer of the present invention.

Referring initially to FIGURES 1-3, the potentiometer of the present invention is generally designated as 10.

Potentiometer Ill comprises a base plate 12 which is a fiat, circular disc of an electrical insulating material, such as a ceramic, glass or plastic. Base plate 12 has a cen- A circular resistance path 18 s provided on the top surface of the base plate IZ concentric with the hole 14 in the base plate. Resistance path 18 may be of any of the well known resistance materials, such as a metal, an alloy of metals, pure carbon, or a mixture of carbon and an insulating material. The resistance path 18 may be applied to the base plate 12 by any well known method, such as painting, spraying or by the deposition from a gas or vapor. The resistance path ll8 is broken to provide two spaced entls. A separate terminal FCice 2 area Zt of an electrically conductive metal, such as silver, is provided on the base plate 12 at each end of the resistance path 18. The notch lt in the edge of the base plate 12 is positioned circumferentially between the terminal areas 2G).

A tubular sleeve 22 of an electrical insulating material, such as a plastic, extends through and has an interference fit with the hole M in the base plate 12. A circular flange 24 extends radially outwardly from one end of the sleeve 22, and, as shown in FIGURE 3, abuts against the bottom surface of the base plate 12. The bore 26 of the sleeve ZZ is threaded.

A resistance path terminal lug, generally designated as 28, is mounted on the top surface of the base plate 12. Terminal lug 28 comprises a flat strip of an electrically conductive metal. At one end the terminal lug 28 has a hole 3h therethrough through which the sleeve 22 extends. The terminal lug 28 extends radially from the sleeve 22 across one of the terminal areas 20 of the resistance path 18, and projects beyond the edge of the base plate 12. The free end of the terminal lug 2% which projects beyond the edge of the base plate 112 is provided with a U-shaped clamping portion 32 which is adapted to receive and be clamped around a Wire. At a point along the length of the terminal lug 28 adjacent the edge of the base plate 112, a finger 34' extends downwardly from the terminal lug into the notch 16 in the base plate 12. The engagement of the finger with the sides of the notch 16 prevents movement of the terminal lug 23 circumferentially across the surface of the base plate lZ. At a point along the terminal lug 28 directly over the terminal area 20, the terminal lug is provided with a rounded depression 36 which engages the terminal area 2h. Thus, the terminal lug 28 is electrically connected to the terminal area 20 so as to form the terminal for one end of the resistance path E8.

A second resistance path terminal lug 38 is mounted on the base plate 12. Terminal lug 38 also comprises a fiat strip of an electrically conductive metal. At one end, the terminal lug 38 has a hole 40 therethrough through which the sleeve 2.2 extends. Terminal lug 38 extends radially from the sleeve 22 across the other terminal area 20 of the resistance path 13, and projects beyond the edge of the base plate 12. The free end of the terminal lug 38, which projects beyond the edge of the base plate 12, is provided with a U-shaped clamping portion 42 which is adapted to receive and be clamped around a wire. At a point along the terminal lug 38 over the terminal area Et) of the resistance path 18, the terminal lug 33 is provided with a relatively fiexibie finger 44 which extends downwardly toward the base plate 12 and longitudinally of the terminal lug 38. The finger 44 engages the terminal area 2h of the resistance path 18 so as to electrically connect the terminal lug 38 to the resistance path 18. Thus, the terminal lug 38 provides the other terminal for the resistance path 18. However, the terminal lug 38 is rotatable about the sleeve 22 so that the finger 44 is slideable along the resistance path lg. A washer fit of an electrical insulating material is mounted around the sleeve 22 between the terminal lug 28 and the terminal lug 38 so as to electrically insulate the etrminal lugs from each other.

A contact plate 48 of an electrically conductive metal is mounted around the sleeve 22 over the terminal lugs 28 and 38. Contact plate 48 has a hole 50 therethrough through which the sleeve 22 extends. A relatively fiexible contact finger 52 extends from an edge of the contact plate 48, and is bent downwardly toward the base plate 12 to engage the resistance path 18. A drive finger 54 extends from another edge of the contact plate 48. The free end portion of the drive finger 54 is bent substantially perpendicularly to the drive plate 48 to extend anonse away from the base plate T2. A washer 56 of an electrical insulating material is mounted around the sleeve 22 etween the drive plate fl and the terminal lug 38. The washer 56 electrically insulates the contact plate 43 from the terminal lug 3%.

A contact terminal lug is mounted around the sleeve 22 over the contact plate 48. Terminal lug 52% comprises a fiat strip of an electrically conductive metal. At one end, the terminal lug 53 is provided With a hole dl) theretl'irough through which the sleeve 22 extends. The terminal lug 58 extends radially from the sleeve 22, and has a U-shaped clamping portion 62 on its free end. The clarnping portion 62 is adapted to receive and be clarnped around a Wire. The terminal lug 53 is in direct contact with the contact plate 48 so as to be electrically connected thereto. Thus, the terminal lug 58 is the terminal for the contact plate 45.

A cylindrieal knob 64 of an electrical insulating material is mounted around the sleeve 22 over the terminal lug 53. The lrnob 64 has a cylindrical passage 66 therethrough into which the sleeve 22 projects. A counterbore 68 is provided in the top of the knob 64. A pair of drive slots 'if' extend diametrically across the top of the knob 64. The slots 7d are adapted to receive a screw driver or similar instrument for rotating the knob 64-. As shown in FGURE 3, the knob 64 is provided With a notch 72 in its outer surface extending from the bottom end thereof. The notch 72 receives the drive finger 54 of the contact plate 48 to provide a drive connection between the knob dd and the contact plate 43. Thus, rotation of the hnob od rotates the contact plate 48 so as to move the contact finger 52 along the resistance path 13.

A screw 74 extends through the knob 64, and is threaded into the threaded bore 2d of the sleeve 22. The head '76 of the screw '7d fit within the counterbore 68 of the knob 6d. A slot 78 extends diametrically across the top surface of the head 76 of the screw '74. The slot 78 is adapted to receive a screw driver or similar instruzent for rotating the screw 74.

The potentiometer of the present invention can be quickly and easily assembled by first inserting the sleeve 22 through the hole M in the base plate 11.2 until the fiange 24 of the sleeve abuts against the bottom surface of the base plate. The terminal lug 28 is then mounted on the sleeve 22 with the finger 34 of the terminal lug 23 extending into the notch T16 in the base plate. This automatically positions the terminal lug 28 so that depression 3d engages a terminal area 2h of the resistance path 18. Then the washer 4-5, terminal lug 33, Washer 56, contact plate 455 and terminal lug 5d are mounted one over the other on the sleeve 22. The knob 64 is then mounted on the sleeve 22 With the drive finger 54 of the contact plate dd fitting into the notch '72 in the knob. Finally, the screw '74 is inserted through the knob 64 and threaded into the sleeve 2.2 to complete the assembly.

In the use of the potentiometer lt) of the present invention, the contact finger S2 can be adjusted to any desired position along the resistance path E8 by first unthreading the screw '74 sliglitly. Then the knob 64 is rotated to rotate the contact plate 48 and slide the contact finger 52 along the resistance path 18. When the contact finger 52 is at the desired position along the resistance path td, the screw T4 is threaded tightly back into the sleeve This clarnps the knob 64, terminal lugs 23, 38 and 58, and the contact plate d tightly between the head '76 of the screw 74- and the base plate .T12 to secure and maintain the contact finger 52 in the desired position along the resistance path E8.

As previously stated, the terminal lug 353 can be rotated about the sleeve 22 to move the finger 44 of the terminal lug 33 along tie resistance path 13. By moving the terminal lug circumferentially along the resistance path E8, the maximum permissible resistance value of the resistance path can be varied. Movement of the terminal lug 33 along the resistance path ll can be easily achieved when the screw '74 is slighlty unthreaded. The movability of the terminal lug 38 also permits the position of the terminal lug to be varied for ease of connecting the terminal lug to other components in a desired circuit. The terminal lug 58 is also movable for this same purpose. Although the clamping portions of the terminal lugs are particularly adapted to be clamped around a Wire, the Wire may be secured to the terminal lugs by soldering, welding or any other means.

Referring to FlGURES 4 and 5, a modification of the potentiometer of the present invention is generally designated as ftl'. Potentiometer id' is substantially identical in construction to the potentiometer 1% of FIGURES 1-3 except that the terminal lugs 28', 38' and 53' are modified to permit the potentiometer E0' to be easily mounted on a printed Circuit board 8h. The terminal tabs 28', 33' and 58' are provided on their free end With mounting pins 32, 84 and 86 respectively which are at right angles to the terminal tabs. The mounting pins, 82, 84 and 8d extend across the peripheral edge of the base plate 12' and project beyond the bottom surface of the base plate.

To mount the potentiometer lit' on the printed circuit board St), the potentiometer N' is seated against the printed circuit board with the mounting pins 82, 8d and 8d extending through holes in the printed circuit board. The monnting pins, 82, 84 and 86 may be soldered to the conductive Circuit strips 88, 9d and 92 respectively on the printed circuit board 8d. Thus, the mounting pins, 82, 84 and f not only physically mount the potentiometer EG' on the printed circuit board ttl, but also electrically connect the terminal tabs 28', 38' and 5d' to the Circuit pattern of the printed Circuit board.

The present invention may be ernbodied in other specific forms Without'departing from the spirit or essential attributes thereof, and accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1..A potentiometer comprising a fiat base plate of an electrical insulating material, said base plate having a hole therethrough, an arcuate resistance path on one surface of said base plate concentric with said hole, said resistance path having a pair of spaced ends, a sleeve of an electrical insulating material secured in the hole in said base plate and projecting above said one surface of said base plate, a pair of resistance element terminal lugs mounted on said sleeve and electrically insulated from each other, each of said resistance element terminal lugs having a portion closely surrounding said sleeve and eX- tending radially from said sleeve over said one surface of the base plate and being electrically connected to separate ends of said resistance path, a contact plate mounted on said sleeve over said resistance element terminal lugs and electrically insulated from the resistance element terminal lugs, a contact finger extending from said contact plate and engaging said resistance path, a contact terminal lugs mounted on said sleeve and electrically contacting said contact plate, said contact terminal lug having a portion closely surrounding said sleeve, a knob mounted on said sleeve and drivingly connected to said contact plate, and screw means threaded longitudinally into the end of said sleeve which is spaced from the base plate, said screw means engaging the knob to clamp said knob, terminal lugs and contact plate together and to said base plate.

2. A potentiometer in accordance with clam 1 in which each of the terminal lugs comprises a fiat strip of metal having a hole therethrough adjacent one end thereof through which the sleeve extends, the diameter of the holes in said terminal lugs being substantially the same as the outer diameter of said sleeve, and means on the 5 other end thereof for connecting the terminal lug into a desired circuit.

3. A potentiometer in accordance with claiin 2 in which the means on each of the terminal lngs for connecting the terminal lug into a circuit comprises a pin extending across the edge of the base plate and beyond the other surface of the base plate.

4-. A potentiometer in accordance with claim 2 in which the base plate has a notch in its edge, said notch being positioned circumerentially between the ends of the resistance path, and one of the resistance element terminal lugs has a finger extending therefrom and projecting into said notch in the base plate to prevent said one resistance element terminal lug from rotating with respect to the base plate.

5. A potentiometer in acccordance with clairn 4 in which a separate terminating area of an electrically conductive material is coating on said base plate at each end of the resistance path, and the one resistance element terminal lug has a detent projecting therefrom and engaging one of said terminal areas.

6. Arpotentiometer in accordance with clairn 5 in which the other resistance element terminal lu g is rotatable t bout the sleeve with respect to the base plate and a finger 6 extends from said other resistance element terminal lug and is adapted to engage the resistance path.

7. A potentiorneter in accordance with clairn 1 in which the drive connection betwee the knob and the contact plate comprises a notch in the knob and a drive finger extending from the contact plate and proiecting into the notch in the knob.

8. A potentiolneter in accordance with clairn l in which the knob has a passage therethrough from its bottom end and a counterbore in its top end, the sleeve projecting into said passage in the l-;nob, and the screw means comprises a screw extending through the knob and having an enlarged head fitting in the counterbore in the knob.

References 'Cited in the file of this patent UNITED STATES PATENTS 

1. A POTENTIOMETER COMPRISING A FLAT BASE PLATE OF AN ELECTRICAL INSULATING MATERIAL, SAID BASE PLATE HAVING A HOLE THERETHROUGH, AN ARCUATE RESISTANCE PATH ON ONE SURFACE OF SAID BASE PLATE CONCENTRIC WITH SAID HOLE, SAID RESISTANCE PATH HAVING A PAIR OF SPACED ENDS, A SLEEVE OF AN ELECTRICAL INSULATING MATERIAL SECURED IN THE HOLE IN SAID BASE PLATE AND PROJECTING ABOVE SAID ONE SURFACE OF SAID BASE PLATE, A PAIR OF RESISTANCE ELEMENT TERMINAL LUGS MOUNTED ON SAID SLEEVE AND ELECTRICALLY INSULATED FROM EACH OTHER, EACH OF SAID RESISTANCE ELEMENT TERMINAL LUGS HAVING A PORTION CLOSELY SURROUNDING SAID SLEEVE AND EXTENDING RADIALLY FROM SAID SLEEVE OVER SAID ONE SURFACE OF THE BASE PLATE AND BEING ELECTRICALLY CONNECTED TO SEPARATE ENDS OF SAID RESISTANCE PATH, A CONTACT PLATE MOUNTED ON SAID SLEEVE OVER SAID RESISTANCE ELEMENT TERMINAL LUGS AND ELECTRICALLY INSULATED FROM THE RESISTANCE ELEMENT TERMINAL LUGS, A CONTACT FINGER EXTENDING FROM SAID CONTACT PLATE AND ENGAGING SAID RESISTANCE PATH, A CONTACT 